1. Field of the Invention
The present invention concerns dispensers which dispense a mixture of fluids, particularly but not exclusively portable dispensers which dispense, under pressure, foam from a mixture of fluids e.g. gas and liquid.
2. The Related Art
The term “portable” as used herein is intended to mean handheld dispensers, preferentially dispensers that can be held with only one hand, such as commercially available dispensers for deodorants, shaving-foam, or liquid cleaning compositions. The invention is also suitable for large portable dispensers, that cannot be held with only one hand.
Foam dispensers to dispense a mixture of liquid and gas as a foam are known. As a common characteristic, they comprise a container and a dispensing cap, said cap comprising a dispensing opening which, at least during dispensing, is in open connection with the upper end of a flow pipe (known as dip tube), of which the opposite end is located near the bottom of the container. Liquid and gas are pushed out of the dispensing opening together due to the pressure difference between the inside and outside of the container. Conveniently the pressurised gas in the containers is air but it may be another suitable gas. The increased or ‘positive’ (relative to external pressure) internal pressure is permanent in pressurised containers. For non-pressurised containers the internal pressure can be decrease/increased manually and temporarily with a pump system to draw air into container and then expel this. Some pump systems raise the internal pressure sufficient to provide for a multitude of dispensing operations. Other pump systems e.g. those forming part of various pump dispensing heads or caps increase internal pressure as part of the dispensing operation. Examples of such dispensing systems are trigger spray heads. Dispensers of this and similar kind are disclosed in U.S. Pat. Nos. 6,053,364, 5,271,530, 5,443,569, etc. One problem with such trigger spray head dispensers is that they are expensive and are not economic in use of plastic resource.
Mist dispensing systems which operate by manual squeezing of a liquid filled flexible-walled container or ‘squeeze bottle’ are also known. Such containers are used for dispensing a mist or spray. Manual compression of the container increases the internal pressure in the head space above the liquid, compelling the liquid to rise upward through the dip tube and be ejected from the container.
Due to the configuration of the cap dispensing orifice and/or the use of two-dimensional structures the liquid can be expelled as a spray.
An exemplary embodiment of such dispenser is shown in U.S. Pat. No. 2,642,313, published in 1953.
Known foam or mist dispensers are sold with a solution inside the container and a flat mesh or net in the flow path of the liquid to form the mist. However, such foam forming elements can be expensive to manufacture and are often not very efficient for creating a desired thick foam.
The present invention seeks to solve or at least reduce the above mentioned problems by the provision of a simple, cost effective foam dispenser which does not require complicated foaming elements in the flow path of the liquid i.e. somewhere in the dip tube that conveys the liquid from the bottom of a container towards the container cap or above the dip tube in the container cap.